In physics, Lami's theorem is an equation relating the magnitudes of three coplanar, concurrent and non-collinear vectors, which keeps an object in static equilibrium, with the angles directly opposite to the corresponding vectors. According to the theorem, where A, B and C are the magnitudes of the three coplanar, concurrent and non-collinear vectors, , which keep the object in static equilibrium, and α, β and γ are the angles directly opposite to the vectors. Lami's theorem is applied in static analysis of mechanical and structural systems. The theorem is named after Bernard Lamy.